BF20 (Butyl Flash 20 mil)  is used to strip in or flash straight window frames, door frames, and other construction seams. BF20 is suitable for both hot and cold temperature ranges, down to 15°F. It is a self-adhering, self-sealing flashing tape consisting of a butyl-based waterproofing coating, laminated to polyethylene film with a 120 day UV exposure rating. The flashing is supplied in rolls, with an easy to remove film release liner and is available in 20 mil thickness and a variety of roll sizes.